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Employee and Agent Benefits (Tables) | 12 Months Ended
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Dec. 31, 2024
Defined Benefit Plans and Other Postretirement Benefit Plans |
Obligations and Funded Status (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Other postretirement |
​ | ​ | Pension benefits | ​ | benefits |
​ | ​ | December 31, | ​ | December 31, |
​ |  | 2024 |  | 2023 |  | 2024 |  | 2023 |
​ | ​ | (in millions) |
Change in benefit obligation | ​ | ​ |  | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Benefit obligation at beginning of year | ​ | $ | (3,390.9) | ​ | $ | (3,209.4) | ​ | $ | (68.4) | ​ | $ | (71.0) | ​
Service cost | ​ | ​ | (59.2) | ​ |  | (55.6) | ​ | ​ | — | ​ |  | — | ​
Interest cost | ​ | ​ | (161.5) | ​ |  | (160.1) | ​ | ​ | (3.2) | ​ |  | (3.4) | ​
Actuarial gain (loss) | ​ | ​ | 199.3 | ​ |  | (119.7) | ​ | ​ | 2.5 | ​ |  | (2.9) | ​
Participant contributions | ​ | ​ | — | ​ |  | — | ​ | ​ | (6.1) | ​ |  | (6.1) | ​
Benefits paid | ​ | ​ | 165.0 | ​ |  | 153.9 | ​ | ​ | 13.6 | ​ |  | 15.0 | ​
Settlement | ​ | ​ | 1.4 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​
Benefit obligation at end of year | ​ | $ | (3,245.9) | ​ | $ | (3,390.9) | ​ | $ | (61.6) | ​ | $ | (68.4) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Change in plan assets | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Fair value of plan assets at beginning of year | ​ | $ | 2,909.6 | ​ | $ | 2,726.3 | ​ | $ | 99.8 | ​ | $ | 94.4 | ​
Actual return on plan assets | ​ | ​ | (14.4) | ​ |  | 258.5 | ​ | ​ | 8.4 | ​ |  | 12.7 | ​
Employer contribution | ​ | ​ | 84.9 | ​ |  | 78.7 | ​ | ​ | 1.3 | ​ |  | 1.6 | ​
Participant contributions | ​ | ​ | — | ​ |  | — | ​ | ​ | 6.1 | ​ |  | 6.1 | ​
Benefits paid | ​ | ​ | (165.0) | ​ |  | (153.9) | ​ | ​ | (13.6) | ​ |  | (15.0) | ​
Settlement | ​ | ​ | (1.4) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​
Fair value of plan assets at end of year | ​ | $ | 2,813.7 | ​ | $ | 2,909.6 | ​ | $ | 102.0 | ​ | $ | 99.8 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Amount recognized in statement of financial position | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Other assets | ​ | $ | — | ​ | $ | — | ​ | $ | 40.4 | ​ | $ | 31.4 | ​
Other liabilities | ​ | ​ | (432.2) | ​ |  | (481.3) | ​ | ​ | — | ​ |  | — | ​
Total | ​ | $ | (432.2) | ​ | $ | (481.3) | ​ | $ | 40.4 | ​ | $ | 31.4 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Amount recognized in accumulated other comprehensive (income) loss | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total net actuarial (gain) loss | ​ | $ | 371.7 | ​ | $ | 425.4 | ​ | $ | (29.9) | ​ | $ | (24.4) | ​
Prior service benefit | ​ | ​ | (53.9) | ​ |  | (70.6) | ​ | ​ | (3.2) | ​ |  | (4.3) | ​
Pre-tax accumulated other comprehensive (income) loss | ​ | $ | 317.8 | ​ | $ | 354.8 | ​ | $ | (33.1) | ​ | $ | (28.7) | ​
​
Components of Net Periodic Benefit Cost (Income) (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension benefits | ​ | Other postretirement benefits |
​ | ​ | For the year ended December 31, |
​ |  | 2024 |  | 2023 |  | 2022 |  | 2024 |  | 2023 |  | 2022 |
​ | ​ | (in millions) |
Service cost | ​ | $ | 59.2 | ​ | $ | 55.6 | ​ | $ | 78.4 | ​ | $ | — | ​ | $ | — | ​ | $ | — | ​
Interest cost | ​ | ​ | 161.5 | ​ | ​ | 160.1 | ​ | ​ | 112.8 | ​ | ​ | 3.2 | ​ | ​ | 3.4 | ​ | ​ | 2.3 | ​
Expected return on plan assets | ​ | ​ | (170.4) | ​ | ​ | (163.2) | ​ | ​ | (178.9) | ​ | ​ | (4.5) | ​ | ​ | (4.6) | ​ | ​ | (4.9) | ​
Amortization of prior service benefit | ​ | ​ | (16.7) | ​ | ​ | (16.8) | ​ | ​ | (16.8) | ​ | ​ | (1.1) | ​ | ​ | (0.8) | ​ | ​ | (1.1) | ​
Recognized net actuarial (gain) loss | ​ | ​ | 39.0 | ​ | ​ | 41.0 | ​ | ​ | 55.7 | ​ | ​ | (0.9) | ​ | ​ | (1.0) | ​ | ​ | (1.1) | ​
Settlement | ​ | ​ | 0.2 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​
Net periodic benefit cost (income) | ​ | $ | 72.8 | ​ | $ | 76.7 | ​ | $ | 51.2 | ​ | $ | (3.3) | ​ | $ | (3.0) | ​ | $ | (4.8) | ​
​ We use the fair market value of assets to determine components of net periodic benefit cost.
Amounts Recognized in Net Periodic Benefit Cost and Accumulated Other Comprehensive (Income) Loss (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension benefits | ​ | Other postretirement benefits
​ | ​ | For the year ended December 31,
​ |  | 2024 |  | 2023 |  | 2024 |  | 2023
​ | ​ | (in millions)
Other changes recognized in accumulated other comprehensive (income) loss | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Net actuarial (gain) loss | ​ | $ | (14.5) | ​ | $ | 24.4 | ​ | $ | (6.4) | ​ | $ | (5.2)
Amortization of gain (loss) | ​ | ​ | (39.0) | ​ |  | (41.0) | ​ | ​ | 0.9 | ​ |  | 1.0
Amortization of prior service benefit | ​ | ​ | 16.7 | ​ |  | 16.8 | ​ | ​ | 1.1 | ​ |  | 0.8
Settlement | ​ | ​ | (0.2) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | —
Total recognized in pre-tax accumulated other comprehensive (income) loss | ​ | $ | (37.0) | ​ | $ | 0.2 | ​ | $ | (4.4) | ​ | $ | (3.4)
Total recognized in net periodic benefit cost and pre-tax accumulated other comprehensive (income) loss | ​ | $ | 35.8 | ​ | $ | 76.9 | ​ | $ | (7.7) | ​ | $ | (6.4)
​
Weighted-Average Assumptions Used to Determine Benefit Obligations (Table) | ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension benefits | ​
​ | ​ | December 31, | ​
​ |  | 2024 |  | 2023 | ​
Discount rate | ​ | 5.50 | % | 4.90 | %
Interest crediting rate - cash balance benefit | ​ | 5.00 | % | 5.00 | %
Rate of compensation increase | ​ | 4.52 | % | 4.56 | %
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Other postretirement benefits | ​
​ | ​ | December 31, | ​
​ |  | 2024 |  | 2023 | ​
Discount rate | ​ | 5.35 | % | 4.80 | %
Rate of compensation increase | ​ | N/A | ​ | N/A | ​
​
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension benefits | ​
​ | ​ | For the year ended December 31, | ​
​ |  | 2024 |  | 2023 |  | 2022 | ​
Discount rate | ​ | 4.90 | % | 5.10 | % | 2.75 | %
Expected long-term return on plan assets | ​ | 6.10 | % | 6.20 | % | 5.20 | %
Interest crediting rate - cash balance benefit | ​ | 5.00 | % | 5.00 | % | 5.00 | %
Rate of compensation increase: | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cash balance benefit | ​ | 4.52 | % | 4.53 | % | 4.59 | %
Traditional benefit | ​ | N/A | % | N/A | % | N/A | %
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Other postretirement benefits | ​
​ | ​ | For the year ended December 31, | ​
​ |  | 2024 |  | 2023 |  | 2022 | ​
Discount rate | ​ | 4.80 | % | 5.00 | % | 2.50 | %
Expected long-term return on plan assets | ​ | 4.65 | % | 5.05 | % | 4.25 | %
Rate of compensation increase | ​ | N/A | ​ | N/A | ​ | N/A | ​
​
Assumed Health Care Cost Trend Rates (Table) | ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, |
​ |  | 2024 |  | 2023 | ​
Health care cost trend rate assumed for next year under age 65 | ​ | 7.50 | % | 7.50 | %
Health care cost trend rate assumed for next year age 65 and over | ​ | 6.50 | % | 6.50 | %
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) | ​ | 4.50 | % | 4.50 | %
Year that the rate reaches the ultimate trend rate (under age 65) | ​ | 2033 | ​ | 2032 | ​
Year that the rate reaches the ultimate trend rate (65 and older) | ​ | 2032 | ​ | 2031 | ​
​
Estimated Future Benefit Payments (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ |  | ​ | ​ | Other postretirement | ​
​ | ​ | ​ | ​ | ​ | benefits (gross benefit | ​
​ | ​ | ​ | ​ | ​ | payments, including | ​
​ |  | Pension benefits |  | prescription drug benefits) |
​ | ​ | (in millions) | ​
Year ending December 31: | ​ | ​ | ​ | ​ | ​ | ​ | ​
2025 | ​ | $ | 227.2 | ​ | $ | 12.6 | ​
2026 | ​ | ​ | 209.3 | ​ | ​ | 11.4 | ​
2027 | ​ | ​ | 219.2 | ​ | ​ | 10.3 | ​
2028 | ​ | ​ | 223.6 | ​ | ​ | 9.2 | ​
2029 | ​ | ​ | 230.8 | ​ | ​ | 8.5 | ​
2030-2034 | ​ | ​ | 1,273.2 | ​ | ​ | 34.0 | ​
​
Defined Benefit Pension Plans Supplemental Information (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the year ended December 31, |
​ | ​ | 2024 | ​ | 2023 |
​ | ​ | Qualified | ​ | Nonqualified | ​ | ​ | ​ | ​ | Qualified | ​ | Nonqualified | ​ | ​ | ​ |
​ |  | Plan |  | Plan |  | Total |  | Plan |  | Plan |  | Total |
​ | ​ | (in millions) |
Amount recognized in statement of financial position | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Other assets | ​ | $ | — | ​ | $ | — | ​ | $ | — | ​ | $ | — | ​ | $ | — | ​ | $ | — | ​
Other liabilities | ​ | ​ | (34.9) | ​ | ​ | (397.3) | ​ | ​ | (432.2) | ​ | ​ | (58.3) | ​ | ​ | (423.0) | ​ | ​ | (481.3) | ​
Total | ​ | $ | (34.9) | ​ | $ | (397.3) | ​ | $ | (432.2) | ​ | $ | (58.3) | ​ | $ | (423.0) | ​ | $ | (481.3) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Amount recognized in accumulated other comprehensive loss | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Total net actuarial loss | ​ | $ | 331.0 | ​ | $ | 40.7 | ​ | $ | 371.7 | ​ | $ | 361.4 | ​ | $ | 64.0 | ​ | $ | 425.4 | ​
Prior service benefit | ​ | ​ | (47.4) | ​ | ​ | (6.5) | ​ | ​ | (53.9) | ​ | ​ | (60.0) | ​ | ​ | (10.6) | ​ | ​ | (70.6) | ​
Pre-tax accumulated other comprehensive loss | ​ | $ | 283.6 | ​ | $ | 34.2 | ​ | $ | 317.8 | ​ | $ | 301.4 | ​ | $ | 53.4 | ​ | $ | 354.8 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Components of net periodic benefit cost | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Service cost | ​ | $ | 55.2 | ​ | $ | 4.0 | ​ | $ | 59.2 | ​ | $ | 51.6 | ​ | $ | 4.0 | ​ | $ | 55.6 | ​
Interest cost | ​ | ​ | 141.6 | ​ | ​ | 19.9 | ​ | ​ | 161.5 | ​ | ​ | 139.7 | ​ | ​ | 20.4 | ​ | ​ | 160.1 | ​
Expected return on plan assets | ​ | ​ | (170.4) | ​ | ​ | — | ​ | ​ | (170.4) | ​ | ​ | (163.2) | ​ | ​ | — | ​ | ​ | (163.2) | ​
Amortization of prior service benefit | ​ | ​ | (12.7) | ​ | ​ | (4.0) | ​ | ​ | (16.7) | ​ | ​ | (12.6) | ​ | ​ | (4.2) | ​ | ​ | (16.8) | ​
Recognized net actuarial loss | ​ | ​ | 35.5 | ​ | ​ | 3.5 | ​ | ​ | 39.0 | ​ | ​ | 38.8 | ​ | ​ | 2.2 | ​ | ​ | 41.0 | ​
Settlement | ​ | ​ | 0.2 | ​ | ​ | — | ​ | ​ | 0.2 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​
Net periodic benefit cost | ​ | $ | 49.4 | ​ | $ | 23.4 | ​ | $ | 72.8 | ​ | $ | 54.3 | ​ | $ | 22.4 | ​ | $ | 76.7 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Other changes recognized in accumulated other comprehensive loss | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Net actuarial (gain) loss | ​ | $ | 5.2 | ​ | $ | (19.7) | ​ | $ | (14.5) | ​ | $ | 9.5 | ​ | $ | 14.9 | ​ | $ | 24.4 | ​
Amortization of net loss | ​ | ​ | (35.4) | ​ | ​ | (3.6) | ​ | ​ | (39.0) | ​ | ​ | (38.8) | ​ | ​ | (2.2) | ​ | ​ | (41.0) | ​
Amortization of prior service benefit | ​ | ​ | 12.7 | ​ | ​ | 4.0 | ​ | ​ | 16.7 | ​ | ​ | 12.6 | ​ | ​ | 4.2 | ​ | ​ | 16.8 | ​
Settlement | ​ | ​ | (0.2) | ​ | ​ | — | ​ | ​ | (0.2) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​
Total recognized in pre-tax accumulated other comprehensive (income) loss | ​ | $ | (17.7) | ​ | $ | (19.3) | ​ | $ | (37.0) | ​ | $ | (16.7) | ​ | $ | 16.9 | ​ | $ | 0.2 | ​
Total recognized in net periodic benefit cost and pre-tax accumulated other comprehensive loss | ​ | $ | 31.7 | ​ | $ | 4.1 | ​ | $ | 35.8 | ​ | $ | 37.6 | ​ | $ | 39.3 | ​ | $ | 76.9 | ​
​
Pension benefits |
Defined Benefit Plans and Other Postretirement Benefit Plans |
Accumulated Benefit Obligation in Excess of Plan Assets (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, |
​ |  | 2024 |  | 2023 |
​ | ​ | (in millions) |
Projected benefit obligation | ​ | $ | 3,245.9 | ​ | $ | 3,390.9 | ​
Accumulated benefit obligation | ​ | ​ | 3,245.9 | ​ |  | 3,390.9 | ​
Fair value of plan assets | ​ | ​ | 2,813.7 | ​ |  | 2,909.6 | ​
Fair Value of Plan Assets (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2024 | ​
​ | ​ | Assets | ​ | Amount | ​ | Fair value hierarchy level | ​
​ | ​ | measured at | ​ | measured at | ​ | ​ | ​
​ |  | fair value |  | net asset value |  | Level 1 |  | Level 2 |  | Level 3 | ​
​ | ​ | (in millions) | ​
Asset category | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Pooled separate account investments: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. large cap equity portfolios (1) | ​ | $ | 236.5 | ​ | $ | — | ​ | $ | — | ​ | $ | 236.5 | ​ | $ | — | ​
U.S. small/mid cap equity portfolios (2) | ​ |  | 98.4 | ​ | ​ | — | ​ |  | — | ​ |  | 98.4 | ​ |  | — | ​
Balanced asset portfolios (3) | ​ |  | 135.0 | ​ | ​ | — | ​ |  | — | ​ |  | 135.0 | ​ |  | — | ​
International equity portfolios (4) | ​ |  | 135.9 | ​ | ​ | — | ​ |  | — | ​ |  | 135.9 | ​ |  | — | ​
Fixed income security portfolios (5) | ​ | ​ | 26.8 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 26.8 | ​ | ​ | — | ​
Real estate investment portfolios (6) | ​ |  | 133.6 | ​ | ​ | — | ​ |  | — | ​ |  | 133.6 | ​ |  | — | ​
Single client separate account investments: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Fixed income securities: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. government and agencies | ​ | ​ | 93.7 | ​ | ​ | — | ​ | ​ | 93.7 | ​ | ​ | — | ​ | ​ | — | ​
States and political subdivisions | ​ | ​ | 15.5 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 15.5 | ​ | ​ | — | ​
Corporate | ​ | ​ | 1,387.2 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,387.2 | ​ | ​ | — | ​
Hedge funds (7) | ​ | ​ | 3.6 | ​ | ​ | 3.6 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​
Mutual funds | ​ | ​ | 109.9 | ​ | ​ | — | ​ | ​ | 109.9 | ​ | ​ | — | ​ | ​ | — | ​
Pooled separate account investment (8) | ​ | ​ | 423.0 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 423.0 | ​ | ​ | — | ​
Other (9) | ​ | ​ | 14.6 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 14.6 | ​ | ​ | — | ​
Total | ​ | $ | 2,813.7 | ​ | $ | 3.6 | ​ | $ | 203.6 | ​ | $ | 2,606.5 | ​ | $ | — | ​
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2023 |
​ | ​ | Assets | ​ | Amount | ​ | Fair value hierarchy level |
​ | ​ | measured at | ​ | measured at | ​ | ​ |
​ |  | fair value |  | net asset value |  | Level 1 |  | Level 2 |  | Level 3 |
​ | ​ | (in millions) |
Asset category | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Pooled separate account investments: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. large cap equity portfolios (1) | ​ | $ | 290.9 | ​ | $ | — | ​ | $ | — | ​ | $ | 290.9 | ​ | $ | — | ​
U.S. small/mid cap equity portfolios (2) | ​ |  | 49.5 | ​ | ​ | — | ​ |  | — | ​ |  | 49.5 | ​ |  | — | ​
Balanced asset portfolios (3) | ​ |  | 97.0 | ​ | ​ | — | ​ |  | — | ​ |  | 97.0 | ​ |  | — | ​
International equity portfolios (4) | ​ |  | 141.8 | ​ | ​ | — | ​ |  | — | ​ |  | 141.8 | ​ |  | — | ​
Fixed income security portfolios (5) | ​ |  | 27.9 | ​ | ​ | — | ​ |  | — | ​ |  | 27.9 | ​ |  | — | ​
Real estate investment portfolios (6) | ​ | ​ | 204.1 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 204.1 | ​ | ​ | — | ​
Single client separate account investments: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Fixed income securities: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. government and agencies | ​ | ​ | 124.9 | ​ | ​ | — | ​ | ​ | 124.9 | ​ | ​ | — | ​ | ​ | — | ​
States and political subdivisions | ​ | ​ | 27.0 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 27.0 | ​ | ​ | — | ​
Corporate | ​ | ​ | 1,394.2 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,394.2 | ​ | ​ | — | ​
Pooled separate account investment (8) | ​ | ​ | 497.9 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 497.9 | ​ | ​ | — | ​
Other (9) | ​ | ​ | 54.4 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 54.4 | ​ | ​ | — | ​
Total | ​ | $ | 2,909.6 | ​ | $ | — | ​ | $ | 124.9 | ​ | $ | 2,784.7 | ​ | $ | — | ​
(1) | The portfolios invest primarily in publicly traded equity securities of large U.S. companies.
(2) | The portfolios invest primarily in publicly traded equity securities of mid-sized and small U.S. companies.
(3) | The portfolios are a combination of underlying fixed income and equity investment options. These investment options may include balanced, asset allocation, target-date and target-risk investment options. Although typically lower risk than investment options that invest solely in equities, all investment options in this category have the potential to lose value.
(4) | The portfolios invest primarily in publicly traded equity securities of non-U.S. companies.
(5) | The portfolios invest primarily in fixed income securities, primarily of U.S. origin. These include, but are not limited to, corporate bonds, residential mortgage-backed securities, commercial mortgage-backed securities, U.S. Treasury securities, agency securities, asset-backed securities and collateralized mortgage obligations.
(6) | The portfolios invest primarily in U.S. commercial real estate properties through a separate account.
(7) | The hedge funds have varying investment strategies that also have a variety of redemption terms and conditions. We do not have unfunded commitments associated with these hedge funds.
(8) | The single client separate accounts invest in a money market pooled separate account.
(9) | Includes cash, net derivative assets (liabilities) and net receivables (payables) for the single client separate accounts.
Target Asset Allocation (Table) | ​
​ | ​ | ​ | ​
Asset category |  | Target allocation | ​
Fixed income security portfolios | ​ | 70 | %
Equity portfolios | ​ | 15 | %
Private investments | ​ | 15 | %
​
Other postretirement benefits |
Defined Benefit Plans and Other Postretirement Benefit Plans |
Fair Value of Plan Assets (Table) | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2024 | ​
​ | ​ | Assets | ​ | Fair value hierarchy level | ​
​ | ​ | measured at | ​ | ​ | ​
​ |  | fair value |  | Level 1 |  | Level 2 |  | Level 3 |
​ | ​ | (in millions) | ​
Asset category | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cash and cash equivalents | ​ | $ | 1.0 | ​ | $ | 1.0 | ​ | $ | — | ​ | $ | — | ​
Fixed income security portfolios (1) | ​ |  | 48.6 | ​ |  | 48.6 | ​ |  | — | ​ |  | — | ​
U.S. equity portfolios (2) | ​ |  | 38.7 | ​ |  | 38.7 | ​ |  | — | ​ |  | — | ​
International equity portfolios (3) | ​ |  | 13.7 | ​ |  | 13.7 | ​ |  | — | ​ |  | — | ​
Total | ​ | $ | 102.0 | ​ | $ | 102.0 | ​ | $ | — | ​ | $ | — | ​
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2023 | ​
​ | ​ | Assets | ​ | Fair value hierarchy level | ​
​ | ​ | measured at | ​ | ​ | ​
​ |  | fair value |  | Level 1 |  | Level 2 |  | Level 3 |
​ | ​ | (in millions) | ​
Asset category | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cash and cash equivalents | ​ | $ | 1.3 | ​ | $ | 1.3 | ​ | $ | — | ​ | $ | — | ​
Fixed income security portfolios (1) | ​ |  | 47.9 | ​ |  | 47.9 | ​ |  | — | ​ |  | — | ​
U.S. equity portfolios (2) | ​ |  | 36.7 | ​ |  | 36.7 | ​ |  | — | ​ |  | — | ​
International equity portfolios (3) | ​ |  | 13.9 | ​ |  | 13.9 | ​ |  | — | ​ |  | — | ​
Total | ​ | $ | 99.8 | ​ | $ | 99.8 | ​ | $ | — | ​ | $ | — | ​
(1) | The portfolios invest in various fixed income securities, primarily of U.S. origin. These include, but are not limited to, corporate bonds, residential mortgage-backed securities, commercial mortgage-backed securities, U.S. Treasury securities, agency securities, asset-backed securities and collateralized mortgage obligations.
(2) | The portfolios invest primarily in publicly traded equity securities of large U.S. companies.
(3) | The portfolios invest primarily in publicly traded equity securities of non-U.S. companies.
Target Asset Allocation (Table) | ​
​ | ​ | ​ | ​
Asset category |  | Target allocation | ​
Fixed income security portfolios | ​ | 50 | %
U.S. equity portfolios | ​ | 35 | %
International equity portfolios | ​ | 15 | %

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